Valve assembly for crimp profile

ABSTRACT

A method of assembling a prosthetic heart valve includes providing a collapsible and expandable stent having an annulus section and an aortic section. The annulus section has a first diameter in a relaxed condition and a second diameter less than the first diameter in a collapsed condition. A constraint is applied to the stent to constrain the annulus section to a predetermined diameter between the first and second diameters. Applying a cuff and/or a plurality of leaflets to the stent in the constrained condition enables less material to be used. The resultant prosthetic valve is therefore able to be collapsed to a smaller diameter for introduction into a patient.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/788,696, filed Mar. 7, 2013, which claims the benefit of the filingdate of U.S. Provisional Patent Application No. 61/666,174 filed Jun.29, 2012, the disclosure of which is hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to heart valve replacement and, inparticular, to collapsible prosthetic heart valves. More particularly,the present invention relates to collapsible prosthetic heart valveshaving a smaller, more consistent diameter.

Prosthetic heart valves that are collapsible to a relatively smallcircumferential size can be delivered into a patient less invasivelythan valves that are not collapsible. For example, a collapsible valvemay be delivered into a patient via a tube-like delivery apparatus suchas a catheter, a trocar, a laparoscopic instrument, or the like. Thiscollapsibility can avoid the need for a more invasive procedure such asfull open-chest, open-heart surgery.

Collapsible prosthetic heart valves typically take the form of a valvestructure mounted on a stent. There are two types of stents on which thevalve structures are ordinarily mounted: a self-expanding stent and aballoon-expandable stent. To place such valves into a delivery apparatusand ultimately into a patient, the valve must first be collapsed orcrimped to reduce its circumferential size.

When a collapsed prosthetic valve has reached the desired implant sitein the patient (e.g., at or near the annulus of the patient's heartvalve that is to be replaced by the prosthetic valve), the prostheticvalve can be deployed or released from the delivery apparatus andre-expanded to full operating size. For balloon-expandable valves, thisgenerally involves releasing the valve, assuring its proper location,and then expanding a balloon positioned within the valve stent. Forself-expanding valves, on the other hand, the stent automaticallyexpands as the sheath covering the valve is withdrawn.

Despite the various improvements that have been made to the collapsibleprosthetic heart valve delivery process, conventional delivery devices,systems, and methods suffer from some shortcomings. For example, inconventional prosthetic valves a cuff and leaflets are attached to thestent, interfering with the full collapsibility of the stent. The cuffand leaflets may include excess tissue material not necessary forfunction. This excess tissue material unduly increases the crimp profileof the valve assembly. It is believed that a large crimp profile may bepartially responsible for vascular injury during delivery of prostheticheart valves. Moreover, slack in the cuff and/or valve assembly reducesthe chronic outward radial force, leading to inferior valve performance.

There therefore is a need for further improvements to the devices,systems, and methods for transcatheter delivery of collapsibleprosthetic heart valves, and in particular, self-expanding prostheticheart valves. Among other advantages, the present invention may addressone or more of these needs.

SUMMARY OF THE INVENTION

A method of assembling a prosthetic heart valve may include providing acollapsible and expandable stent having an annulus section and an aorticsection, the annulus section having a first annulus diameter in arelaxed condition and a second annulus diameter less than the firstannulus diameter in a collapsed condition. A constraint may be appliedto the stent to constrain the annulus section to a predetermined annulusdiameter between the first annulus diameter and the second annulusdiameter. At least one of a cuff or a plurality of leaflets may beassembled to the constrained annulus section to form a prosthetic heartvalve and the constraint may be removed from the stent after theassembly step.

In some examples, the aortic section has a first aortic diameter in therelaxed condition and a second aortic diameter less than the firstaortic diameter in the collapsed condition, and the step of applying theconstraint constrains the aortic section to a predetermined aorticdiameter between the first aortic diameter and the second aorticdiameter.

The constraint may include a first suture tied to the annulus section ofthe stent to constrain the diameter of the annulus section to thepredetermined annulus diameter and a second suture tied to the aorticsection of the stent to constrain the diameter of the aortic section tothe predetermined aortic diameter. The predetermined annulus diametermay be between about 85% and about 95% mm of the first annulus diameter.The constraint may include at least one drawstring to constrain thediameter of the annulus section. The at least one drawstring may includea first suture tied to the annulus section of the stent to constrain thediameter of the annulus section to the predetermined annulus diameter.

In some examples, the removing step may include cutting the first sutureto release the annulus section to an unconstrained annulus diameterbetween the predetermined annulus diameter and the first annulusdiameter. The constraint may include at least one ring disposed about acircumference of the stent to constrain the diameter of the stent. Theconstraint may also include a first ring disposed about the annulussection of the stent and a second ring disposed about the aortic sectionof the stent. The first ring and the second ring may be coupled togetherby a helical portion.

In some examples, further comprising rotating the constraint withrespect to the stent to facilitate the assembling step. The constraintmay include a cylindrical body having a proximal opening, a distalopening, a lumen defined between the proximal opening and the distalopening, and at least one window in the body configured and arranged topermit assembly of the prosthetic heart valve therethrough. The at leastone window may include three triangular windows evenly spaced about thecircumference of the constraint. The constraint may include a coneportion at the distal opening. Cutouts in the body may be spaced tofacilitate assembly of the heart valve. The constraint may furtherinclude at least two rings and a plurality of angled struts coupled tothe at least two rings, the plurality of angled struts outlining aplurality of triangles.

A method of assembling a prosthetic heart valve includes providing acollapsible and expandable stent having an annulus section and an aorticsection, the annulus section having a first annulus diameter in arelaxed condition and second annulus diameter less than the firstannulus diameter in a collapsed condition. The stent may be cooled to atemperature below a predetermined temperature at which the diameter ofthe annulus section decreases to a predetermined diameter between thefirst and second diameters. At least one of the cuff or a plurality ofleaflets may be assembled to the cooled stent to form a prosthetic heartvalve.

In some examples, the step of cooling the stent may include placing thestent within a cooled air box. The predetermined temperature may bebelow the Austenitic Finish temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described herein withreference to the drawings, wherein:

FIG. 1 is a partial side elevational view of a prosthetic heart valveincluding a stent and a valve assembly having a cuff and leaflets;

FIG. 2 is schematic perspective view of a prosthetic heart valve in acooled air box;

FIG. 3 is a side perspective view of a fixation device having two rings;

FIGS. 4A and 4B are side perspective views of fixation devices havingtwo rings coupled to a helical portion;

FIG. 5A is a side perspective view of a prosthetic heart valveconstrained with drawstrings at the annulus section;

FIG. 5B is a side perspective view of a prosthetic heart valveconstrained with drawstrings at the annulus section and the aorticsection;

FIG. 6 is a side perspective view of a fixation device having acylindrical body and a substantially triangular window;

FIG. 7 is a side perspective view of a fixation device having a body, acone portion and multiple windows;

FIG. 8 is a side perspective view of a fixation device having a bodywith internal cutouts, and multiple windows;

FIG. 9 is a side perspective view of a fixation device having a pair ofrings and angled struts; and

FIG. 10 is a side perspective view of a fixation device having threerings and angled struts.

Various embodiments of the present invention will now be described withreference to the appended drawings. It is to be appreciated that thesedrawings depict only some embodiments of the invention and are thereforenot to be considered limiting of its scope.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “proximal,” when used in connection with aprosthetic heart valve, refers to the end of the heart valve closest tothe heart when the heart valve is implanted in a patient, whereas theterm “distal,” when used in connection with a prosthetic heart valve,refers to the end of the heart valve farthest from the heart when theheart valve is implanted in a patient.

FIG. 1 shows a collapsible prosthetic heart valve 100 according to anembodiment of the present disclosure. The prosthetic heart valve 100 isdesigned to replace the function of a native aortic valve of a patient.Examples of collapsible prosthetic heart valves are described inInternational Patent Application Publication No. WO/2009/042196; U.S.Pat. Nos. 7,018,406; and 7,329,278, the disclosures of all of which arehereby incorporated herein by reference. As discussed in detail below,the prosthetic heart valve has an expanded condition and a collapsedcondition. Although the invention is described herein as applied to aprosthetic heart valve for replacing a native aortic valve, theinvention is not so limited, and may be applied to prosthetic valves forreplacing other types of cardiac valves.

The prosthetic heart valve 100 includes a stent or frame 102, which maybe wholly or partly formed of any biocompatible material, such asmetals, synthetic polymers, or biopolymers capable of functioning as astent. Suitable biopolymers include, but are not limited to, elastin,and mixtures or composites thereof. Suitable metals include, but are notlimited to, cobalt, titanium, nickel, chromium, stainless steel, andalloys thereof, including nitinol. Suitable synthetic polymers for useas a stent include, but are not limited to, thermoplastics, such aspolyolefins, polyesters, polyamides, polysulfones, acrylics,polyacrylonitriles, polyetheretherketone (PEEK), and polyaramides. Thestent 102 may have an annulus section 110, an aortic section 111 (FIG.5A), and a transition section (not shown) disposed between the annulusand aortic sections. Each of the annulus section 110 and the aorticsection 111 of the stent 102 includes a plurality of cells 112 connectedto one another around the stent. The annulus section 110 and the aorticsection 111 of the stent 102 may include one or more annular rows ofcells 112 connected to one another. For instance, the annulus section110 may have two annular rows of cells 112. When the prosthetic heartvalve 100 is in the expanded condition, each cell 112 may besubstantially diamond shaped. Regardless of its shape, each cell 112 isformed by a plurality of struts 114. For example, a cell 112 may beformed by four struts 114.

The stent 102 may include commissure features 116 connecting at leasttwo cells 112 in the longitudinal direction of the stent 102. Thepurpose of the commissure features 116 will become apparent from thedescription below.

The prosthetic heart valve 100 also includes a valve assembly 104attached inside the annulus section 110 of the stent 102. United StatesPatent Application Publication No. 2008/0228264, filed Mar. 12, 2007,and United States Patent Application Publication No. 2008/0147179, filedDec. 19, 2007, the entire disclosures of both of which are herebyincorporated herein by reference, describe suitable valve assemblies.The valve assembly 104 may be wholly or partly formed of any suitablebiological material, polymer, fabric or other suitable fiber. Examplesof biological materials suitable for the valve assembly 104 include, butare not limited to, porcine or bovine pericardial tissue. Examples ofpolymers suitable for the valve assembly 104 include, but are notlimited to, polyurethane, ultra-high-molecular-weight polyurethane andpolyester.

The valve assembly 104 may include a cuff 106 disposed on the luminalsurface of annulus section 110, on the abluminal surface of annulussection 110, or on both surfaces, and the cuff may cover all or part ofeither or both of the luminal and abluminal surfaces of the annulussection. The cuff and/or the sutures used to attach the valve assembly104 to stent 102 may be formed from or includeultra-high-molecular-weight polyethylene. FIG. 1 shows cuff 106 disposedon the luminal surface of annulus section 110 so as to cover part of theannulus section while leaving other parts thereof uncovered. The cuff106 may be attached to stent 102 by one or more strings or suturespassing through the cuff and around selected struts 114 of the stent.The valve assembly 104 may further include a plurality of leaflets 108which collectively function as a one-way valve. A first edge 122 of eachleaflet 108 may be attached to the stent 102 between two adjacentcommissure features 116 by any suitable attachment means, such assuturing, stapling, adhesives or the like. For example, the first edge122 of each leaflet 108 may be sutured to the stent 102 by passingstrings or sutures through the cuff 106 of the valve assembly 104. Theleaflets 108 may be attached to the stent 102 along at least some struts114 of the stent and through the eyelets in the commissure features 116to enhance the structural integrity of the valve assembly 104. A secondor free edge 124 of each leaflet 108 may coapt with the correspondingfree edges of the other leaflets, thereby enabling the leaflets tofunction collectively as a one-way valve.

As shown in FIG. 1, at least one leaflet 108 may be attached to thestent 102 so that its first edge 122 is disposed substantially alongspecific struts 114 a, 114 b, 114 c, 114 d, 114 e and 114 f located inthe annulus section 110 of the stent. That is, the edge 122 ispositioned in substantial alignment with struts 114 a, 114 b, 114 c, 114d, 114 e, and 114 f. Struts 114 a, 114 b, and 114 c may be connected toone another in substantially end-to-end fashion diagonally along threecells 112, beginning with an end of the strut 114 a connected to acommissure feature 116 and ending with an end of strut 114 c connectedto an end of strut 114 d. Struts 114 c and 114 d are part of the samecell 112 and may collectively define a substantially right angle betweenthem. Struts 114 d, 114 e, and 114 f may be connected to one another insubstantially end-to-end fashion diagonally along three cells 112,beginning with an end of the strut 114 f connected to a commissurefeature 116 and ending with the connection between the end of strut 114c and the end of strut 114 d.

As discussed above, the leaflets 108 may be attached directly to andsupported by the struts 114 a, 114 b, 114 c, 114 d, 114 e, and 114 f,and by commissure features 116, such as by suturing. In such event, thecuff 106 may perform little or no supportive function for the leaflets108. Hence, the cuff 106 is not subjected to high stresses and istherefore less likely to wear during use. In light of this, thethickness of the cuff may be reduced. Reducing the thickness of the cuff106 results in a decrease in the volume of the valve assembly 104 in thecollapsed condition (e.g., every mm of diameter is a 3 fold decrease involume of cuff circumferentially and possible a smaller leaflet since itdoes not have to be as large to be assembled at a larger diameter). Thisdecreased volume is desirable as it enables the prosthetic heart valve100 to be implanted in a patient using a delivery device that is smallerin cross-section than conventional delivery devices. In addition, sincethe material forming the stent struts 114 is stronger than the materialforming the cuff 106, the stent struts 114 may perform the supportivefunction for the leaflets 108 better than the cuff 106.

The volume of the valve assembly 104 may be further reduced by havingthe cuff 106 cover only a portion of the surface of annulus section 110.With continued reference to FIG. 1, the first or proximal end 118 of thecuff 106 may substantially follow the contour of the first or proximalend 119 of the stent 102. As such, the proximal end of the cuff 106 mayhave a generally sinusoidal or zigzag shape. This eliminates any freeedge of the cuff 106, which otherwise might extend directly between thecusps of the cells 112 at the proximal end 119 of the stent 102, andenables the entire length of the proximal end 118 of the cuff 106 to besecured to the stent 102. The second or distal end 120 of the cuff 106,on the other hand, may be disposed substantially along at least somestruts 114, but not necessarily the struts in a single annular row ofcells 112. More particularly, the distal end 120 of the cuff 106 mayfollow the stent struts 114 up to the commissure features 116, such thatthe cuff covers all of the cells 112 in the bottom annular row 113 ofcells and in a second annular row 115 of cells located between thecommissure features and the proximal end 119 of the stent 102, butcovers a lesser area of cells in the annular regions between thecommissure features. In other words, the distal end 120 of the cuff 106may be disposed substantially along struts 114 a, 114 b, 114 e, 114 f,114 g and 114 h, as shown in FIG. 1. Strut 114 g may be connected at oneend to strut 114 h, and at the other end to the intersection of struts114 b and 114 c. Strut 114 h may be connected at one end to strut 114 g,and at the other end to the intersection of struts 114 d and 114 e.Struts 114 c, 114 d, 114 g, and 114 h collectively form a single cell112.

As a result of the foregoing configuration, all of the cells 112 in thebottom annular row 113 of cells may be entirely covered by the cuff 106.The cuff 106 may also entirely cover those cells 112 in the secondannular row 115 that are located directly below the commissure features116. All of the other cells 112 in the stent 102 may be open or notcovered by the cuff 106. Hence, there may be no cells 112 which are onlypartially covered by the cuff 106.

Since the edges of the valve leaflets 108 extend up to the secondannular row 115 of cells 112 only in the regions of the commissurefeatures 116, there is little to no likelihood of leakage in the area ofthe cells between the commissure features in the second annular row ofcells, and therefore no need for the cuff 106 to cover this area. Thisreduction in the area of the cuff 106, both at the proximal end 118 andat the distal end 120 thereof, reduces the amount of material in thevalve assembly 104, thereby enabling the prosthetic valve 100 to achievea smaller cross-section in the collapsed condition.

In operation, the embodiments of the prosthetic heart valve describedabove may be used to replace a native heart valve, such as the aorticvalve, a surgical heart valve or a heart valve that has undergone asurgical procedure. The prosthetic heart valve may be delivered to thedesired site (e.g., near a native aortic annulus) using any suitabledelivery device, including the delivery device described in detailbelow. During delivery, the prosthetic heart valve is disposed insidethe delivery device in the collapsed condition. The delivery device maybe introduced into a patient using a transfemoral, transapical ortransseptal approach. Once the delivery device has reached the targetsite, the user may deploy the prosthetic heart valve described above.Upon deployment, the prosthetic heart valve expands into secureengagement within the native aortic annulus. When the prosthetic heartvalve is properly positioned inside the heart, it works as a one-wayvalve, allowing blood to flow in one direction and preventing blood fromflowing in the opposite direction.

As previously discussed, a large valve diameter will lead to a largecrimp profile and possible vascular injury during implantation of theprosthetic heart valve. One way to reduce the valve crimp profile is toeliminate unneeded tissue from the valve. Since the diameter of thevalve when fully deployed and operating within the native valve annulusof the patient is typically smaller than the fully expanded diameter ofthe valve when built, excess valve tissue will typically be present whenthe valve is built using conventional techniques.

The following describes new methods and devices for pre-assembling orbuilding a prosthetic heart valve at a smaller, constrained diameter toreduce this excess valve tissue. By building the heart valve at aconstrained diameter, less tissue is used. When the constraint isremoved, the valve does not expand to the fully expanded diameter of thestent, but rather expands to an intermediate diameter based on theamount of tissue used. This intermediate diameter is larger than thediameter of the native valve annulus so that a sufficient outward radialforce is exerted on the valve annulus to hold the valve in place, but iscloser to the size of the native valve annulus than the fully expandeddiameter of the stent. Moreover, by building the heart valve at aconstrained diameter, less material is used, allowing for a reducedcrimp profile. In addition, building the prosthetic heart valve usingthese methods produces a more consistent valve diameter.

FIG. 2 illustrates one method of building the prosthetic heart valvewithout physically constraining the valve. The stent 102 of theprosthetic heart valve 100 may be formed of a shape-memory material,such as nitinol, having properties that are dependent on the temperatureof the material. As a result, the shape of stent 102 is temperaturedependent. Prosthetic heart valve 100 may be built inside a cooled airbox 250, the temperature and/or humidity of which may be displayed ondisplay 270 and adjusted using dials 260. The desired temperature withincooled air box 250 may be chosen based on the material of stent 102. Forexample, cooled air box 250 may allow a user or technician to assemble aprosthetic heart valve 100 below room temperature. In some examples,heart valve 100 may be assembled in a cooled air box 250 at atemperature below the Austenite Finish temperature. In at least someexamples, assembly is performed at a temperature of between 18 and 22°C. Due to this cold temperature, stent 102 may assume a diameter duringassembly that is smaller than its diameter at room temperature. Afterassembly, the stent 102 is removed from cooled air box 250 and, as thestent gradually returns back towards its austenite finish transitiontemperature, it will return to the intended heat-set shape. However, thetissue assembled to the stent 102 may constrain this expansion, and theassembled valve may only expand to an intermediate diameter.Alternatively, heart valve 100 may be built via dipping in hot or coldsaline to set the shape, then assembling at room temperature.

Instead of using cooled air box 250, the prosthetic heart valve 100 maybe physically constrained prior to and during assembly so that lesstissue or material is used to form the valve. FIG. 3 illustrates afixation device 300, which includes a pair of rings 310 that may be usedto constrain the valve. Each ring 310 may be made of suitable syntheticpolymers including, but not limited to, thermoplastics, such aspolyolefins, polyesters, polyamides, polysulfones, acrylics,polyacrylonitriles, polyetheretherketone (PEEK), and polyaramides. Forexample, rings 310 may be formed of silicone.

Prior to attaching the leaflets 108 or the cuff 106, rings 310 may beplaced over the stent 102 to constrain the stent to a first diameterthat is less than the fully expanded diameter. The fully expandeddiameter, for example, on a valve labeled “29 mm” may be slightly higherthan 29 mm, (e.g., 29-30 mm). The use range of this valve may be in therange of about 25 mm to 27 mm so as to have 2-4 mm of interference withthe anatomy to have enough radial force to stay in place. The builddiameter may be selected between the stent parent diameter and the highuse range (e.g., 25-30 mm in this case). The build diameter may vary foreach valve size. Thus, rings 310 may constrain the stent 102, forexample, to a diameter of between about 85% and about 95% of the fullyexpanded diameter.

Two rings 310 may be used to constrain the stent 102, one at the annulussection 110 and another at the aortic section 111. The rings 310 mayalso be disposed near the commissure features 116 or anywhere on thestent as desired. It will be understood that a single ring 310 ormultiple rings such as three, four or five rings may be used toconstrain the stent. Rings 310 may be slid up or down the stent 102 toallow the user or technician to couple the leaflets 108 and/or cuff 106to the stent, such as by sewing. Rings 310 may also be slid out of theway to clip or remove excess tissue or material from the cuff 106, theleaflets 108 or both.

FIG. 4A illustrates a fixation device 400 for aiding in the assembly ofa prosthetic heart valve in accordance with another embodiment of theinvention. Fixation device 400 includes a pair of rings 410 joined toone another by a helical portion 420. The rings 410 may be disposedaround the annulus section 110 and aortic section 111 of a stent 102.Because the two rings 410 are connected, fixation device 400 may bebetter secured to the stent during assembly. If helical portion 420impedes assembly of the valve, fixation device 400 may be simply rotatedaround the stent 102 to better allow the user to see the valve, attachtissue or material to the stent, or trim excess material from the cuff(if necessary). In this manner, fixation device 400 may be graduallyrotated around the stent 102 as the operator assembles the leaflets 108or the cuff 106 to the stent. In another example, shown in FIG. 4B,fixation device 400 includes a pair of rings 410 joined to one anotherby three connecting struts 425. It will be understood that rings 410 maybe joined by one, two, three, four, five or more struts 425.

FIGS. 5A and 5B illustrate methods of constraining the prosthetic heartvalve 100 using drawstrings 510. Drawstrings 510 may be formed ofsutures or straps that tie around a portion of the stent 102 duringassembly. As seen in FIG. 5A, a pair of drawstrings 510 may be tiedaround the annulus section 110 of the stent 102 during assembly. Thedrawstrings 510 may act to constrain the stent to a desired diameteruntil assembly has been compeleted. After assembly of the prostheticheart valve 100, the drawstrings may be severed and removed. FIG. 5Billustrates a similar example of constraining the prosthetic heart valve100 using drawstrings 510. The example of FIG. 5B utilizes threedrawstrings 510 at the annulus section 110 of stent 102 and a fourthdrawstring 510 near the aortic section 111. It will be understood thatany number of drawstrings 510 may be used as desired to constrain theheart valve 100 during assembly. Moreover, it will be understood thatthe drawstrings may be tied around any portion of the stent 102,including the annulus section 110, transition section, aortic section111 and/or the commissure features 116 (if any), and may be tied aroundor weaved through any portion of the stent such as, for example, thestruts 114.

FIG. 6 illustrates a fixation device 600 for facilitating the assemblyof a prosthetic heart valve in accordance with a further embodiment ofthe invention. Fixation device 600 may include a generally cylindricalbody 610 having a proximal opening 620, a distal opening 630 and a lumen640 extending between the proximal and distal openings. Body 610 may beprovided with a large window 650 extending from proximal opening 620toward distal opening 630. Window 650 may have a relatively large widthat the proximal opening 620, and may gradually narrow toward the distalopening 630 so as to define a generally triangular shape.

The lumen 640 through body 610 may be sized to receive a valve supportstent 102. Specifically, stent 102 may be placed within the lumen 640 offixation device 600 to constrain it to a first diameter during assemblyof prosthetic valve 100. With stent 102 assembled in fixation device600, window 650 provides access to the stent to enable the operator tosew, or otherwise assemble the valve leaflets 108 and/or cuff 106thereto. Access to different regions on the circumference of stent 102may be had simply by rotating the stent within fixation device 600 untilthe desired region is aligned with window 650. Alternatively, body 610may include multiple windows 650 around its circumference. The windows650 may be spaced equally or unequally around the circumference of body610, as desired, in order to provide access to different regions ofstent 102 needed to complete the assembly process. Moreover, windows 650need not be generally triangular, but may be of any shape or size, suchas circular, ovoid, rectangular, square or any other suitable shape.Where fixation device 600 includes multiple windows 650, the size andshape of the windows may all be the same, some may be the same, or theymay all be different from one another.

FIG. 7 illustrates a variation of fixation device 600. Similar tofixation device 600, fixation device 700 may include a generallycylindrical body 710 having a proximal opening 720, a distal opening 730and a lumen 740 extending between the proximal and distal openings. Thelumen 740 may be sized to receive a stent 102. Specifically, stent 102may be placed within the lumen 740 of fixation device 700 to constrainit to a first diameter during assembly of prosthetic valve 100. Body 710may have three triangular windows 750 disposed 120° apart. An additionalcone portion 760 may be provided adjacent the distal opening 730 of body710. The tapered walls of cone portion 760 may facilitate the loading ofa stent 102 into lumen 740. Additionally, cone portion 760 may be sizedto allow the aortic section 111 of stent 102 to be seated within itduring assembly.

In another variation, shown in FIG. 8, a fixation device 800 is similarto fixation device 700 with one primary difference. Rather than havingsolid wall structures between adjacent windows 850, as is the case infixation device 700, the body 810 of fixation device 800 includesinternal cutouts 870 between windows 850 to provide greater access tostent 102 to enable the operator to sew or otherwise attach the valveleaflets 108 and/or cuff 106 thereto. The resulting fixation device 800includes a cone portion 860 and a body 810 formed by a plurality ofstrut members joined to the cone portion to form triangular shapes. Itwill be understood that rather than a cone portion 860, fixation device800 may include a conventional ring.

Another fixation device 900 in accordance with the present invention isillustrated in FIG. 9. Fixation device 900 includes a body 910 having aproximal opening 920, a distal opening 930 and a lumen extending betweenthe proximal and distal openings. Body 910 may include horizontal strutsforming a top ring 960 a adjacent the distal open end 930, whichcorresponds to the aortic section 111 of stent 102, and horizontalstruts forming an intermediate ring 960 b intermediate the proximal anddistal openings, which corresponds to the transition section or annulussection of the stent. Intermediate ring 960 b may be continuous ordiscontinuous as seen in FIG. 9, and may be used to align the prostheticheart valve 100 within fixation device 900, such as by aligning thecommissure features 116 of the valve with portions of the intermediatering. Fixation device 900 may be formed with any desirable distancebetween rings 960 a and 960 b. Joined to rings 960 a, 960 b are aplurality of angled struts 970. With the exception of intermediate ring960 b, body 910 and angled struts 970 may be formed similar to body 810such that angled struts 970 essentially form three inverted trianglesdisposed around the circumference of fixation device 900.

FIG. 10 illustrates a fixation device 1000 similar the fixation device900 of FIG. 9. Fixation device 1000 includes a body 1010 having aproximal opening 1020, a distal opening 1030 and a lumen extendingbetween the proximal and distal openings. Body 1010 may include threerings, including a top ring 1060 a corresponding to the aortic section111 of a constrained stent 102, an intermediate ring 1060 bcorresponding to the transition section of a constrained stent and abottom ring 1060 c corresponding to the annulus section 110. It will beunderstood that fixation device 1000 may be formed with any desiredspacing between the three rings 1060. Joined to rings 1060 are aplurality of angled struts 1070, similar to those shown in the examplesabove.

Using the cooled air box 250 or any of the fixation devices describedabove, a user or operator is able to assemble a prosthetic heart valveat a diameter that is smaller than the fully expanded diameter of stent102. When the assembled valve is removed from the cooled air box or thefixation device, it does not expand to the fully expanded diameter ofthe stent, but rather expands to an intermediate diameter based on theamount of tissue used. This intermediate diameter allows less materialto be used for the cuff and leaflets of the valve, enabling the valve tobe crimped to a smaller profile, thereby facilitating its introductioninto and deployment in a patient.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims. For example,features of the drawstring examples may be combined with a fixationdevice into a single embodiment. Moreover, a cooled air box may be usedto assemble a prosthetic heart valve according to any of the precedingexamples. Additionally, the constraint may be useful for assembling orconstructing not only heart valves, such as transcatheter aortic valveimplants, but also surgical valves, annuloplasty rings and the like. Seeabove comments on diameters. It should also be noted in embodimentsincluding constraints having rings that the top and bottom rings neednot be of the same diameter. Moreover, while certain embodiments havebeen described using the word “ring,” it will be understood that theterm “ring” is not limited to a closed shape and that C-shapedconfigurations are also contemplated, for example. It will beappreciated that the various dependent claims and the features set forththerein can be combined in different ways than presented in the initialclaims. It will also be appreciated that the features described inconnection with individual embodiments may be shared with others of thedescribed embodiments.

The invention claimed is:
 1. A constraint for assembling a prostheticheart valve including a collapsible and expandable stent having anannulus section, the annulus section having a first annulus diameter ina relaxed condition and a second annulus diameter less than the firstannulus diameter in a collapsed condition, the constraint comprising: acylindrical body having a proximal opening, a distal opening, and alumen defined between the proximal opening and the distal opening andsized to constrain the annulus section to a predetermined annulusdiameter between the first annulus diameter and the second annulusdiameter, the body further comprising at least one window configured andarranged to permit assembly of the prosthetic heart valve therethrough.2. The constraint of claim 1, wherein the constraint further comprises acone portion at the distal opening.
 3. The constraint of claim 1,wherein the constraint comprises three rings.